Remove env dump by every worker in debug mode

It pollutes debug log making it unuseable for debugging.
Add debug messages around server disconnection
Refactor resize test so size can be easily changed

Useful during debugging, when running with a set size of 1 reduces debug
output.
Test death by signal, as well as worker.destroy()

Previous test only tested worker.kill() (which is === worker.destroy()),
an does not guarantee child is actually killed with a signal.
Merge pull request #28 from strongloop/feature/test-worker-sigkill

Feature/test worker sigkill